In an electromagnetic relay which is used inside a circuit of a high voltage battery of an electric vehicle or large-sized direct current device etc., sometimes the arc discharge which occurs at the time the contacts are opened (hereinafter simply referred to as an “arc”) causes the conduction state to be maintained and prevents the circuit from being broken. Further, even if the circuit is broken, the arc sometimes causes wear of contacts or melting of the contacts or other problems. Therefore, to secure the performance which is demanded from an electromagnetic relay which is used for a direct current high voltage circuit, it is essential to improve the arc extinguishing performance. Patent documents 1 to 4 disclose electromagnetic relays which are provided with devices for extinguishing the arcs which are generated at the time the contacts open or methods of extinguishing the arcs.
Patent document 1 discloses a method of extinguishing an arc which is generated in a space which is formed when a moving contact separates from a fixed contact when the moving contact and the fixed contact are opened (hereinafter referred to as a “contact gap”) by using permanent magnets to apply magnetic force in a perpendicular direction to the arc so as to pull the arc from a contact portion to a non-contact portion and thereby extend the arc length and smoothly cut the arc. However, with the method of Patent document 1, just the magnetic forces of permanent magnets are used to make the arc move from a contact portion to a non-contact portion, so the permanent magnets which are required for extinguishing the arc becomes larger and, along with this, the electromagnetic relay itself becomes larger in size.
Further, Patent document 2 discloses a plunger-type potential relay which has a ceramic plate chamber which faces a contact gap and which is provided by indentation, in the axial direction, of the surface of the inside wall of the housing present at a position perpendicular to the pole face of a permanent magnet and which has an arc resistance plate which has a ceramic as a material embedded in the ceramic plate chamber. With the method of Patent document 2, an arc-resistance plate is set at the place to which the arc moves, so sufficient stretching of the arc length is obstructed. Further, if arranging the arc resistance plate further separated from the contact gap so as to secure sufficient stretching of the arc length, the contact becomes larger in size.
Patent document 3 discloses a sealed contact device which provides an arc extinguishing grid near a moving contact and a fixed contact. The arc extinguishing grid of the sealed contact device of this third patent literature is one where “several to several tens of 0.2 to 0.3 mm or so metal sheets are stacked. Between the individual metal sheets, there is a gap of several mm. These metal sheets, as shown in FIG. 3, are supported by support plates 38, 40 (39, 41) which are comprised of ceramic etc. and are arranged as shown in FIG. 2”. Support plates for superposition of the metal sheets with gaps between them become further necessary, so the contact becomes larger in size.
Patent document 4 discloses a sealed contact device which seals in hydrogen gas or another electrical insulating gas and operates the contact inside a hermetically formed sealed container. The cooling ability of the electrical insulating gas and the arc extinguishing action of permanent magnets which are arranged outside of the sealed container are used to quickly extinguish the generated arc. The method of Patent document 4 requires equipment for sealing in hydrogen gas or another electrical insulating gas. To prevent the electrical insulating gas from passing through, it is necessary to seal the container by a metal, ceramic, etc. Therefore, the cost rises.